As announced in September, the Gentoo in the Cloud AMIs have been retired. Since January 2014, the Gentoo in the Cloud AMIs have been succeeded by the Pygoscelis Papua Linux AMIs, which are our newer unofficial Gentoo builds. The Pygoscelis Papua Linux AMIs will continue to built.
The Gentoo in the Cloud AMIs have been removed from all the regions except us-east-1, where they will remain for archival purposes. If you wish to copy any of the old images, our articles HowTo: Copy EC2 EBS AMIs Between Accounts and HowTo: Move an EC2 EBS AMI From One Region to Another may be of use.